(function() {
var ready = {
	colum: 10,
	row: 15,
	cellWidth: 32,
	cellHeight: 32,
	bulletW: 4, //bullet width
	bulletH: 4, //bullet height
	bs: 20, //bulletSpeed
	check: 3
};

var status = {};
var ImageFile = ["rocket", "bullet", "monster"];
var images = {};

var showbg = function() {
	var bottom = ready.height + ready.cellHeight - status.currentTop;
	if(bottom) {
		status.ctx.drawImage(status.bgCtx.canvas, 0, status.currentTop, ready.width, bottom, 0, 0, ready.width, bottom);
	}
	if(ready.height - bottom) {
		status.ctx.drawImage(status.bgCtx.canvas, 0, bottom);
	}
};

